Ques 3.

The average of 20 numbers is zero. Of them, how many of them may be greater than zero, at the most?

Solution

→ Average of 20 numbers is 0.
→ Sum of 19 positive number is X.
→ 20th number be -X.
→ So, the average is 0. 19 numbers are positive.

Ques 4.

The captain of a cricket team of 11 members is 26 years old and the wicket keeper is 3 years older. If the ages of these two are excluded, the average age of the remaining players is one year less than the average age of the whole team. Find out the average age of the team.

Solution

→ Average age of the team is X.
→ Sum of the age of all the 11 members = 11X
→ Age of captain = 26
→ Age of wicket keeper = 29
→ Average age of 9 remaining members = (11X – (26+29))/9 = (X-1)
→ Solving this we get X = 23 years.

Ques 5.

The library has an average of 510 visitors on Sundays and 240 on other days. What is the average number of visitors per day in a month of 30 days beginning with a Sunday?

Solution

→ In a month of 30 days beginning with a Sunday, there will be 4 complete weeks and another two days which will be Sunday and Monday.
→ Hence there will be 5 Sundays and 25 remaining days in a month begin with Sunday.
→ Average visitors in a month of 30 days = (510*5) + (240*25)/30 = 285.
So, the average visitors in a month of 30 days is 28

Ques 6.

The average age of husband, wife and their child 3 years ago was 27 years and that of wife and the child 5 years ago was 20 years. What is the present age of the husband?